Nylon Spur Gear 55mm Dia G.T.B. - 1 (Blue) are the most usable type of gears. Spur Gear 55mm Dia G.T.B. - 1 (Blue) have straight teeth, and are mount on parallel shaft. Sometimes, many Spur Gear 55mm Dia G.T.B. - 1 (Blue) are use at once to create very large gear reductions. These gears mesh together correctly only if they fit to parallel shafts. No axial thrust is created by the tooth loads. Spur gears are excellent at moderate speeds but tend to be noisy at high speeds. Robu.in